The present invention relates to electromagnetic transponding devices and, more particularly, a device for monitoring and measuring distance.
Electromagnetic transponding devices having receivers and transmitters are well known in the art. One specific application for such devices is for training dogs and other pets to remain within a certain bounded area without the need for fences or other physical structures. For example, U.S. Pat. No. 4,967,695 to Giunta discloses a system for controlling the movement of dogs having a loop of wire that serves as a transmitting antenna and defines the boundary of the desired area. Giunta further discloses a receiver attached to the dog's collar that produces a signal, such as an electric shock, when the dog moves into the vicinity of the loop of wire. The Giunta device determines when the dog is in the vicinity of the loop by comparing the magnitude of the received signal. Specifically, as the dog moves closer to the loop of wire, the magnitude of the signal increases. When the magnitude reaches a certain threshold, the dog is considered to be within the vicinity of the loop, and the receiver produces the electric shock or similar signal.
This type of monitoring is in a class called ‘amplitude detection’. The detected proximity of the units is based upon the strength of the transmitter and sensitivity of the receiver. The accuracy and precision of the measured distance is a percentage of the total range of the system.
The disadvantage with conventional systems such as that disclosed by Giunta and others is that installation and set up is labor intensive and time consuming. Specifically, a trench must be dug around the perimeter of the desired area, and a wire loop must be installed. Additionally, the receiver must be programmed for the specific loop to set the desired boundaries. Also, the system is stationary and not designed for mobile use. Thus, there is a need in the art for an improved system for monitoring and controlling the movement of dogs and other animals.
A more accurate method of measurement is to detect the phase of a signal. For example, U.S. Pat. No. 5,661,460 to Sallen discloses a system that compares the received signal to a reference. However, this method is actually a time delay to a code epoch that is RF power-detected and does not include a quadrature phase to provide greater resolution and accuracy.
Additionally, there is a need for adapting such a system to be used with other applications, such as monitoring the location of children, properly placing road signs, and measuring distance on a golf course. Presently, most prior art systems rely on advanced technology including global positioning systems (GPS) to monitor the location of children or determine the proper position of a road sign. Other systems use laser beams which, when reflected off remote objects, can be used to monitor and measure distances. While these systems are very accurate, they require the use of expensive and sophisticated electronic equipment. Accordingly, there is a need in the art for a cost effective system of monitoring and measuring distances.
Therefore, a principal object of this invention is to provide a system that monitors and measures distance in a simplified manner.
Another object of the present invention is to provide a system that monitors and measures distance in a mobile situation.
Yet another object of this invention is to provide a system that monitors and measures distance for training and controlling the movement of dogs and other animals.
A further object of this invention is to provide a system that monitors and measures distance for safely monitoring the location of children.
Still a further object of this invention is to provide a system that monitors and measures distance for placing road signs and the like.
Also, an object of this invention is to provide a system that monitors and measures distances for applications that require one-foot precision and accuracy.
These and other objects will be apparent to those skilled in the art.